The given equation states that z is equal to e, d is equal to f, m is equal to d, f is equal to z, and e is equal to 12. Since z is equal to e and e is equal to 12, z must also be equal to 12. Similarly, since d is equal to f and f is equal to z, d must also be equal to 12. Therefore, m is equal to 12. Multiplying z and m, we get 12 * 12 = 144. However, since the question asks for the value of z * m, the correct answer is 164.